Biology and Epidemiology of the Rabies Virus

1. Biology and Epidemiology of the Rabies Virus Rachel Radcliffe, DVM, MPH CDC Career Epidemiology Field Officer Division of Infectious Disease Epidemiology

2. Objectives • Describe epidemiology of rabies virus • Describe transmission and pathogenesis of rabies virus • Outline management of animals potentially exposed to rabies • Outline management of animals that potentially expose humans to rabies

3. The Rabies Virus • Lyssavirus of the Rhabdoviridae family • Bullet-shaped, RNA virus • Infects only mammals • Various strains of rabies virus exist

4. Rabies Epidemiology — World • >55,000 deaths worldwide • Mainly Africa and Asia • 60–70% of human cases are children 5–15 years of age • ~98% of human cases caused by dog bites

5. Rabies Epidemiology — United States • Human rabies deaths relatively rare • 4 deaths in 2009 • >90% of animal rabies cases occur in wildlife • 6,690 animal rabies cases in 2009 • 92% wildlife animals • 8% domestic animals • Rabies annual prevention costs ~$300 million

7. Rabies Epidemiology — West Virginia • Most animal rabies cases occur in wildlife • Cat most common domestic animal to be rabies-positive • Raccoon-strain rabies endemic to eastern portion of state • Bat strain found throughout state • Most cases occur during warm-weather months

8. Counties with Confirmed Cases of Raccoon Strain Rabies In West Virginia, 2001–2010 HANCOCK BROOKE OHIO MARSHALL MORGAN BERKELEY MONONGALIA WETZEL MARION MINERAL PRESTON TYLER PLEASANTS HAMPSHIRE TAYLOR 2 DODD- HARRISON WOOD RIDGE RITCHIE BARBOUR TUCKER GRANT JEFFERSON HARDY WIRT LEWIS UP- GILMER CAL- SHUR JACK- RANDOLPH HOUN SON MASON ROANE PENDLETON BRAXTON WEBSTER PUTNAM CLAY CABELL KANAWHA POCAHONTAS NICHOLAS LINCOLN WAYNE BOONE FAYETTE GREENBRIER LOGAN MINGO RALEIGH SUM- MERS MONROE WYOMING MERCER McDOWELL Counties with Raccoon-Strain Rabies

13. Rabies Transmission • Saliva from bite of infected animal • Scratch • Theoretical risk • Saliva or neural tissue contact with mucous membrane (mouth, nose) • Saliva or neural tissue introduced into fresh, open wound* * Fresh, open wound is defined as wound that has bled in past 24 hours

14. Rabies Pathogenesis • Virus introduced through bite wound, open skin wound, or mucous membrane • Travels along nerves from site of bite to brain • Virus multiplies in brain leading to inflammation • Virus moves from brain to salivary glands and saliva where virus is shed

15. Rabies Pathogenesis • Virus introduced through bite wound, open skin wound, or mucous membrane • Travels along nerves from site of bite to brain • Virus multiplies in brain leading to inflammation • Virus moves from brain to salivary glands and saliva where virus is shed

16. Rabies Incubation Period • Time between bite and appearance of symptoms • Weeks to months • No risk of rabies transmission from infected animal during incubation period • Used to establish confinement periods for animals exposed to potentially rabid animals

17. Rabies Diagnosis • Animal diagnosis • Post-mortem testing • Direct Fluorescent Antibody (DFA) test • Antigen of virus in brain tissue • Human diagnosis • Several tests required for ante-mortem diagnosis • Saliva, serum, cerebrospinal fluid, hair follicle from nape of neck

18. Rabies Treatment and Prevention in Humans • No effective treatment once clinical signs appear • Rabies post-exposure prophylaxis (PEP) given before onset of symptoms is nearly 100% effective • Rabies PEP • Wound cleansing • Rabies Immunoglobulin (RIG) • Rabies Vaccination • No time limit to give PEP

19. Rabies PEP — Wound Cleansing • Should occur as quickly as possible after wound received • Soap and water or povidone-iodine

20. Rabies PEP — RIG • Given only once with first vaccine dose • If not given with first vaccine dose, can be given up to 7 days after first vaccine dose received • If person has previously received PEP or pre-exposure prophylaxis, RIG should not be given

21. Rabies PEP — Vaccination • Previously unvaccinated persons get 4 doses • Days 0, 3, 7, and 14 • 5th dose dropped from vaccine schedule last year • Intramuscular injections • Previously vaccinated persons get 2 doses • Days 0 and 3 • No RIG given

22. Rabies Pre-exposure Prophylaxis • Recommended for certain high-risk groups • Veterinarians, wildlife biologists, animal control personnel • 3 vaccine doses • Days 0, 7, and 21 or 28 • Does not eliminate need for medical care after an exposure

23. Rabies Treatment and Prevention in Animals • No treatment for animal rabies • No post-exposure prophylaxis for animals • Routine vaccination is the only way to prevent animal rabies • Vaccination schedule for dogs and cats • First vaccine at 3 months of age • Booster vaccine 1 year later • Vaccinate every 3 years after this

24. Management of Animals Potentially Exposed to Rabies • Vaccinated cats, dogs, ferrets • Rabies booster immediately • 45 day observation • Under owner’s control • Any sign of illness should be reported and animal evaluated by a veterinarian

25. Management of Animals Potentially Exposed to Rabies • Unvaccinated dogs, cats, ferrets • Euthanasia • Strict isolation for 6 months • Confinement in an enclosure that precludes direct contact with people or other animals • Rabies vaccine upon entry or 1 month prior to release • Any sign of illness should be reported and animal evaluated by a veterinarian

26. Management of Animals Potentially Exposed to Rabies • Expired vaccinations in dogs, cats, ferrets • Evaluated on a case-by-case basis • Information to consider • Severity of exposure • Time lapsed between vaccinations • Number of previous vaccinations • Current health status • Rabies epidemiology

27. Management of Animals Potentially Exposed to Rabies • Vaccinated livestock • Rabies booster vaccine immediately • 45 day observation • Multiple rabid animals in a single herd is unusual • Restriction of entire herd usually not necessary • Coordinate with WV Dept. of Agriculture

28. Management of Animals Potentially Exposed to Rabies • Unvaccinated livestock • Euthanasia • Confined under close observation for 6 months • Any signs of illness should be reported and animal euthanized and tested for rabies • Vaccination during confinement can be done • Coordinate with WV Dept. of Agriculture

29. Management of Animals Potentially Exposed to Rabies • Other animals • Consider on case by case basis • Euthanasia generally recommended

30. Management of Animals that Potentially Expose Humans • Dogs, Cats, Ferrets • Owned animals should be observed for 10 days • Rabies vaccination not recommended during this time • Strays should be euthanized and tested • 10 day quarantine can be done if resources allow • If not available for testing, PEP should be considered based on rabies epidemiology of area, bite circumstances, etc.

31. Management of Animals that Potentially Expose Humans • Exotic mammalian pets • No established rabies observation period for animals except dogs, cats, ferrets • Consider on case-by-case basis • Information to consider • Type of animal • Rabies epidemiology of area • Bite circumstances

32. Management of Animals that Potentially Expose Humans • Livestock • Not high risk for transmitting rabies • Healthy and available animals can be observed for 14 days • Unknown shedding period of rabies virus in saliva • Euthanasia and testing is other option • Coordinate with WV Dept of Agriculture

33. Management of Animals that Potentially Expose Humans • Wildlife • If available, euthanize and test immediately • If unavailable, PEP should be considered based on • Type of animal • Rabies epidemiology of area • Bite circumstances

34. Management of Animals that Potentially Expose Humans • Small mammals are considered low risk for rabies • Not been found to cause human rabies in US • PEP not usually recommended for these exposures unless animal was sick and rabies activity is high in the area • Groundhogs/woodchucks may pose greater risk • Special consideration for bats

35. Rabies Resources • www.cdc.gov/rabies • ACIP recommendations • Compendium of Animal Rabies Prevention and Control, 2008 • WV Rabies Surveillance, Management, and Control Manual (DC-4)

36. Rabies Summary • Human rabies rare in US and WV • Most rabies cases occur in wildlife in US and WV • Transmission occurs through introduction of infectious saliva or neural tissue into the body • Human prevention based on rabies PEP • Animal prevention based on rabies vaccination

37. Animal Management Summary • Management of animals potentially exposed to rabies depends on vaccination status and type of animal exposed • Management of animals that expose humans to rabies depends on type of animal, ownership status of animal, and other factors